Growth Performance of Black poplar (Populus nigra L.) Under Drought Condition and Sewage Water Irrigation

The response of black poplar (Populus nigra L.) seedlings to the combination of both drought and sewage water irrigation have been investigated from 18-5-2019 to 18-8-2019. Two drought stress levels; D0; 90% or full water holding capacity (WHC) and D1; 30% WHC interacted with three sewage irrigation treatments; S0; 100 % of tap water as a control, S1; 50% of tap water and sewage water and S2; 100% of sewage water. The irrigation water quality index (IWQI) of S1 was 59.31 located under moderate restrictions class for irrigation purposes. Despite to its low pollution load index (PLI); 0.47. Fully irrigation to soil holding capacity with S1 (S1D0) led to a significant increase in seedling height, stem base diameter, fresh and dry biomass and moisture content in shoot system. In addition, the highest tolerance index (TI %) about 92.07 % of the seedlings recorded despite to the soil toxicity with Ni and Pb ions. Lowest accumulation and metal toxicity of Cu, Zn, Cd, Pb and Mn in the soil and leaves have been determined. Thus, diluting sewage water; 1:1 can be used to irrigate black poplar trees with high water demand and moderate to high tolerance to salts for reforestation and urban vegetation.